Question: At what time did L'Hospitalet de Llobregat have a population of 250,536?
Paraphrase: When did L'Hospitalet de Llobregat reach a population of 250,536?
SPARQL (Wikidata): SELECT ?value WHERE { wd:Q15470 p:P1082 ?s . ?s ps:P1082 ?x filter(contains(?x , '250536.0')) . ?s pq:P585 ?value}